Plasma reactors are employed for processing workpieces such as semiconductor wafers, by carrying out such processes as plasma enhanced chemical vapor deposition, plasma enhanced etching, plasma enhanced physical vapor deposition, among various examples. The reactor may maintain a plasma inside its chamber by capacitive coupling of RF plasma source power. Typically, such capacitive coupling involves the use of the reactor chamber ceiling as a ceiling electrode driven by an RF source power generator, while other components of the reactor chamber, including the chamber side wall, are grounded. Process gas may be introduced into the chamber through a gas distribution showerhead included in the ceiling electrode. The process gas may be supplied through an internal conduit within the grounded chamber side wall. A supply conduit extends between the side wall and the ceiling showerhead. Depending upon the amount of RF source power applied to the ceiling electrode, the path traveled by the process gas from the side wall to the ceiling electrode has a very large voltage difference, sufficient to ignite plasma within the supply conduit if the voltage drop is non-uniform. Therefore, there is a need to provide a smooth voltage drop along the length of the supply conduit.